Advances in technology have resulted in smaller and more powerful computing devices. For example, there currently exist a variety of portable personal computing devices, including wireless computing devices, such as portable wireless telephones, personal digital assistants (PDAs), and paging devices that are small, lightweight, and easily carried by users. More specifically, portable wireless telephones, such as cellular telephones and internet protocol (IP) telephones, can communicate voice and data packets over wireless networks. Further, many such wireless telephones incorporate other types of devices, e.g., a wireless telephone can also include a digital still camera, a digital video camera, a digital recorder, and an audio file player. Such wireless telephones can process executable instructions, including software applications, such as a web browser application, that can be used to access the Internet. As such, these wireless telephones can include significant computing capabilities.
An equivalent isotropic radiation power (EIRP) value refers to a highest signal strength measured in any direction from a transmitter device (e.g., a transmitter integrated into a wireless telephone). In jurisdictions that have EIRP limitations imposed by regulatory bodies (e.g., the Federal Communications Commission (FCC) in the United States), wireless devices (e.g., a transmitter device) are required to comply with EIRP limitations when transmitting via a single antenna or multiple antennas. For example, a transmitter device operating in the 6-9 gigahertz (GHz) frequency band (e.g., an ultra-wide band (UWB)) must adhere to stringent EIRP limitations. To comply with the EIRP limitations in the United States, a transmitter device operating in the 6-9 GHz frequency band may be required to have a power spectral density less than −14 dBm (an abbreviation of a power ratio in decibels (dB) of a measured power referenced to one milliwatt (mW)) in a 500 megahertz (MHz) bandwidth in a frequency band of interest (e.g., the 6-9 GHz frequency band).
An EIRP value is associated with a product of an input power to an antenna of the transmitter device and an antenna radiation pattern associated with the antenna. The EIRP value may be an average EIRP across multiple symbols over a time period (e.g., one millisecond in the United States) that is determined based on a measured signal strength in all directions from the transmitter device (e.g., a wireless device). In the United States, the EIRP value of the transmitter device is an average value of the signal strength measured over one millisecond. The average EIRP may be referred to as an EIRP pattern which is representative of a measured radiation pattern of a multi-antenna transmission. For example, the transmitter device may be tested in accordance with procedures specified in Part 15.31(a) and 15.523 of FCC rules. When the average EIRP value in any direction is determined to be above an EIRP limit, a power level of the transmitter device must be reduced by an amount that the average EIRP value was over the limit. The average EIRP value may be measured for a particular bandwidth (BW) (e.g., an EIRP BW) that corresponds to a particular EIRP limit. For example, when the antenna radiation pattern (of a single antenna or of an antenna array) is not spatially flat (e.g., spatially smooth), a peak antenna gain in a single direction (that is in excess of the EIRP limit) causes a reduction of transmit power in all directions.